1. Field of the Invention
The present invention relates to a drive apparatus for an extruder, which is a large-scale multiple-shaft screw type extruder for melting, kneading, and extruding synthetic resin material. More particularly, the present invention relates to an improvement in realizing the operation over a wide range of screw rotary speeds by a switching lever at the primary motor, allowing a high speed and a low speed running.
2. Description of the Related Art
Generally, a synthetic resin material is melted, kneaded, and extruded by a screw type extruder in order to carry out kneading/mixing for improving quality or physical properties the synthetic resin material after compounding reaction or reaction treatment such as regeneration. A multiple-shaft (usually two shafts) screw type extruder, which has excellent kneading function, has been adopted for the screw type extruder so that the size thereof increases. As the size of such a twin screw type extruder increases, a size of a drive apparatus for an extruder also increases. The drive apparatus includes a speed reduction mechanism unit and an output distributing mechanism unit. The speed reduction mechanism is designed to be able to change its speed such that the screw type extruder can change its rotary speed for different materials or changes in the physical property of the material. Each of the speed reduction mechanism and the output distributing mechanism unit comprises a large number of gears and gear shafts. Such drive apparatus has large overall size and weight as compared with the body of the twin screw type extruder.
As a countermeasure against increasing the size of the drive apparatus, adoption of a planetary gear speed reduction mechanism for the speed reduction mechanism unit has been proposed in order to reduce the size. Namely, JP-A-2001-1913921 discloses a configuration in which the speed reduction mechanism unit includes a planetary gear speed reduction mechanism at a front stage and a parallel-shaft gear speed reduction mechanism at a rear stage, wherein the planetary gear speed reduction mechanism and the parallel-shaft gear speed reduction mechanism are arranged in series and integrated to the output distributing mechanism unit. In the planetary gear speed reduction mechanism at the front stage, a main motor with a constant speed is connected to the supporting shaft of a sun gear through a gear connector, an auxiliary motor with variable speed is connected through a plurality of gears to the outer wall of a hollow gear, which has gear teeth on its inner and outer walls and is rotatably supported, and a pinion holder for the planetary gear is connected to an input shaft of a parallel shaft gear speed reduction mechanism at the rear stage through another gear connector. At the rear stage, an output shaft of the parallel shaft gear speed reduction mechanism, which is driven by a set of speed reduction gears, constitutes a main output shaft of the output distributing mechanism. A plurality of sets of speed reduction gears for the parallel shaft gear speed reduction mechanism are prepared, and can be interchanged in order to change the speed reduction ratio as needed.
Related drive apparatus configured as described above presents the following problems. The speed reduction mechanism unit is composed of two stages of speed reduction mechanisms. Thus, the size of the drive apparatus increases such that a large installing space may be required. Further, the speed reduction mechanism unit and the output distributing mechanism unit are integrated to each other. In the case of such a large machine, transportation for delivery becomes difficult because of the overall size and weight. The driver may be delivered in a state dismantled by frame division and reassembled at an installing place. However, reassembling of the gear machine requires a very sophisticated technique. Thus, it is difficult to reassemble the gear machine at the installing place.